The present invention relates to a process for producing a solid cosmetic, involving subjecting a cosmetic base containing appropriate amounts of an oil and a powder as principal ingredients to an injection molding directly in a mold or through ogive mold, capsule, inner plate, container, or the like fitted in the mold. The molded product thus obtained has no unevenness in hardness in the interior thereof and possesses a polymorphous property which permits forming into any desired shape, further possessing a shape retaining property and a sufficient strength. In actual use, the solid cosmetic thus obtained adheres well to the skin and spreads to a satisfactory extent. Moreover, it does not provide a dry or sticky impression, possesses a good cosmetic retaining property, and does not re-adhere to handkerchief, tableware, etc. Further, the molded product exhibits an extrenmely good handleability and the high productivity.
Heretofore, there have been proposed a solvent process wherein a cosmetic base and a volatile solvent are mixed together into a slurry, then the slurry is filled into a container or a mold, thereafter the solvent is removed, followed by solidifying molding (Japanese Patent Laid Open No. 127305/1981) wherein a cosmetic base and a volatile solvent are mixed together into a slurry, then the solvent is absorbed by an absorber while the slurry, which is viscous, is injected at a low pressure, followed by filling and solidifying.
Also, as methods wherein ogive mold, capsule, inner plate, container, or the like, are fitted into a mold and then a cometic base is filled into the thus-loaded member to obtain a molded product, there are known a compression molding wherein an inner plate is fitted into a mold, an injection molding wherein a cosmetic base is injected through an opening formed in the back of a container or an inner plate, a cast molding wherein a cosmetic base is filled by casting into an inner plate or a container to obtain a solid cosmetic, and a method (Japanese Patent Laid Open No. 62513/1984) wherein a cosmetric base is filled by casting into a cylindrical container, then taken out and cut into an appropriate thickness, and the thus-cut piece is filled into a container and pressed at a low pressure to obtain a solid cosmetic. For example, according to the compression molding, an inner plate is loaded to a female mold of a pressing machine and a cosmetic base is filled into the inner plate, thereafter pressure is applied from one side by means of a male mold to obtain a solid cosmetic.
As injection molding methods of injecting a cosmetic base through a small opening formed in the back of a container or an inner plate, there have been proposed a method (Japanese Patent Publication No. 54766/1988) wherein a cosmetic base is dissolved in a solvent and thereby made viscous, then this viscous cosmetic base is injected through a small opening formed in the back of a container or an inner plate and thereafter solidified while the solvent is sucked from the cosmetic base and a method (Japanese Patent Laid Open No. 156709/1988) wherein a viscous cosmetic base is injected through a small opening formed in the back of a container and then solidified by cooling using a cooling plate from the surface opening side of the container.
Solid cosmetics obtained by compression molding are simple in shape and their shapes are limited to planar shapes. When complicated shapes, e.g. spherical and rod-like shapes are to be obtained, compression becomes non-uniform, and during molding and when the cosmetics are applied to the skin, there occurs breakage or cracking. Besides, such cosmetics are unsatisfactory also in the feeling of use such as being low in strength and inferior in both impact strength and adhesion to the skin or to a puff. Also as to the amount of a binder which is used for remedying these drawbacks, there is a limitation. If the amount of the binder is increased, the fluidity of the cosmetic base used is deteriorated, resulting in that the filling thereof into the inner plate from the hopper is no longer smooth, thus causing unevenness in weighing. Thus, in compression molding, there is a restriction not only in the shape of a cosmetic to be obtained but also in point of formulation and it is extremely difficult to produce a solid cosmetic capable of satisfying all of high strength, good feeling of use and desired shape which are important conditions required for cosmetics.
According to a cast dissolving/melting filling method, in the case of filling and molding a cosmetic base into a container or an inner plate, since the filling pressure is low, the cosmetic base to be filled is limited to one which assumes a liquid state of low viscosity when melted. The use of a highly viscous and sticky cosmetic base makes the filling thereof impossible and thus there is a restriction on the formulation of a cosmetic base to be used.
According to a solvent method wherein a cosmetic base which has been dissolved in a solvent is injected and filled and solidified while the solvent is sucked in vacuum, a high strength is obtained when the amount of a binder used is large, but the user feels the cosmetic sticky, and with the lapse of time, the cosmetic will be twisted and cause unevenness. In addition, it becomes necessary to use a special apparatus for recovery of the solvent, thus resulting in increase of the cost. Further, the suction of the solvent causes unevenness in the amount of the binder and that of a coloring matter in the cosmetic, thus making it extremely difficult to effect the filling of the cosmetic in a constant amount. And the injection pressure is as low as 4 to 6 kg/cm.sup.2. Thus, this method is unsuitable for the filling of a highly viscous, clay-like cosmetic base and requires a large amount of a solvent for lowering the viscosity. Besides, the resulting molded product is poor in strength.
According to the method wherein a cosmetic base is filled under pressure through a small hole formed in the back of a container and just thereafter cooling is performed using a cooling plate from the surface opening side of the container, since the cooling just after the filling is only at the surface opening portion of the container, the cooling efficiency is low and it takes time until solidifying by the cooling. Thus, not only the productivity is low but also molded products obtained by this method are limited to thin products. Further, since the cosmetic composition used should have fluidity at the time of melting, if the amount of a binder used is large, a restriction is imposed on the formulation, the cosmetic is sticky in use and will be twisted with the lapse of time, causing unevenness.
According to a method wherein a cosmetic composition is cast into a tubular container, then taken out from the tube and cut in round slices, which slices are each filled into a container, followed by pressing at a low pressure, there are the same drawbacks as in the foregoing cast molding method; besides, the process up to completion of the molding is complicated, leading to an increase of the manufacturing cost.
It is the object of the present invention to provide a process for producing a solid cosmetic which has remedied the above-mentioned drawbacks of the prior art.